17. Acute Induction of Heme Oxygenase-1 in Rat Liver by a Whole-body X-ray Irradiation
Keiko Suzuki, Masahiko Mori, Fumihiko Kugawa* and Hiroshi Ishihara
(*Nihon Univ.)
Keywords: heme oxygenase, X-rays, liver
The transcription of the heme oxygenase-1 (HO-1) gene is enhanced by various stimuli, such as oxidative stress, UVA radiation and heat shock, and a considerable body of evidence has confirmed that the HO-1 gene is cytoprotective against numerous stresses. The HO-1 gene is also commonly called Hsp (heat shock protein) 32. In mammals, biliverdin, which is one of the products of an enzyme reaction by heme oxygenase, is subsequently converted to bilirubin by biliverdin reductase. Both biliverdin and bilirubin are powerful antioxidants. Another product of the enzyme reaction by heme oxygenase is carbon monoxide, which is considered to be a promising and significant messenger molecule in the soluble guanylate cyclase (sGC)-cGMP system.
No immediate early effect of radiation upon the induction of HO-1 enzyme has been characterized, yet. Now, in the present study we have provided evidence that the heme oxygenase-1 enzyme is induced by ionizing radiation in rat liver within a few hours.
When male Wistar MS strain rats (8 weeks) received whole-body X-ray irradiation of 17.0 Gy, the activity of heme oxygenase in the liver was significantly enhanced (2.5 times) 7 h later (Fig.16). Western blotting of the irradiated liver demonstrated a significant increase in the level of HO-1 protein. The level increased 2 h after the irradiation, reached a peak at 4 h, and then decreased gradually until 10 h, when it was still higher than the control level. Thus, X-rays were confirmed to be stressors that induce acute HO-1 expression transiently in the liver.
|